Re: Atomic filesystem or not

[David Masover <ninja@slaphack.com>]

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As I understand it:

Claudio Martins wrote:

| is said that reiser4 is atomic what it means is that each low level
operation
| on the filesystem either happens or not at all. That means that each
block

Each low-level request is automatically an atom, but...

|   As far as I understand this is the guarantee that reiser4 gives. For
the cp
| to happen entirely or not at all it would have to be one big atomic
request
| only, but I think that kind of operation might only be possible using the
| special reiser4 system call in development.

Indeed, the "special reiser4 system call" should support building bigger
atoms.

In fact, I suspect that if reiser4 is accepted as a defacto standard,
then it's even likely that someone would implement some library for
doing atomic operations -- because a system call named "reiser4" is not
portable to other filesystems.  For instance, I believe someone's done a
filesystem based on MySQL, which has atomic operations -- but would
probably want a whole different interface for doing them.

If such a library were developed, and had at least one stable backend
(reiser4), then I think it'd be very likely for standard utils such as
'cp' to support it.



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